The art of completing wells to exclude solids particles produced by well fluids is commonly known in the literature as gravel packing.
It is common practice in the construction of wells bored into the earth to dispose steel casing or other tubular conduits inside of the well. In some well constructions the casing is grouted into the bore by placing portland cement in the annular space between the casing and the well bore. The casing can be deployed through the depth where the productive subterranean formation or plurality of formations is encountered below the surface. In the former the well completion is referred to those familiar with the art of well completions as open hole completions, whereas those well completions where the casing and cement is run through or past the depth of the productive formation is known to those familiar with the art of well completions as cased holes. In either case of open hole completions or cased hole completions it is well practised art to dispose across the production formation depths sand screens, slotted pipes, or pipes with holes pre-perforated at surface into the well casing on a second continuous tube known in the literature as production tubing.
Production tubing is disposed inside of the casing extending from the surface to a depth closer to the production formation. It is often desirable to place a packer on the end of the production tubing to force well fluids up the tubing and avoid fluids being produced up the casing. The production tubing is then a removable pipe that is disposed in wells generally in jointed lengths of 40 feet (about 12 m), but can be deployed as a continuous tubing string in what is commonly known in the oil and gas industry as continuous tubing. It is common practice to deploy in production tubing string various apparatus to allow for well fluid control. It is also common to control such devices from surface using electrical and hydraulic tubes disposed simultaneously with the production tubing and connected to the outer diameter of the production tubing. These hydraulic tubes are known to those familiars with the art of well completions as control lines.
In the cased hole completions it is common practice to run explosive charges into the well after the casing is cemented across the productive formation depths and perforate holes through the casing and cement into the productive formation to create a path for fluid flow into the well.
In many wells either in cased or open hole completions unwanted formation solids are produced into the well along with the production fluids. These solids are often undesirable and many methods of stopping these solids from flowing into the well whilst producing the fluids are well defined in the literature as the art sand control. One of the more familiar methods of stopping solid flow is to perform a gravel pack.
A gravel pack is performed by placing a known size of sand, which is referred to as the gravel, into the well across the production formation to create a filter medium to stop or reduce the flow of solid materials from the formation into the well. The gravel is most commonly prohibited from flowing into the well by a device commonly know as a well screen. The well screens are designed to keep the specialized sand mesh, known as the gravel, in place in the annular space between the casing or well bore outside of the screens forming the filter media.
The current methods of placing a gravel pack is requires that the screens be deployed in the well on a tubing string from surface until the screens are at the depth of the producing formation. At this point sand is placed around the screens by various methods of pumping, circulating, and other wise dispose sand around the screens. Once the sand is placed around the screens the tubing string is detached from the screens and extracted from the well. Thereafter the production tubing with packers, control lines, sliding sleeves, and packers are disposed in the well above the screens. Hence the screens are detached from the production string in the common known methods of the industry.
It is current practice to build the well screens out of wire wrap welded to bars running parallel to the screen axis and said bars are placed around a pipe extending the length of the screen with holes through the pipe. This pipe is commonly known to those familiars with the art as the base pipe and forms the structure to which the wire wrap and welded bars are attached. Hence the commonly known well screen consists of wire wrap helically wrapped around the circumference of the screen attached to welded bars that are fitted onto the outer diameter of base pipe. In other designs of sand screens the screen is manufactured with sintered materials located between the wire wrap or in some cases outside of the wire wrap. In all cases the screen has an inner pipe base that holes or other geometric penetrations to allow fluids to flow into the screens inner diameter.
The well screen lengths disposed in wells vary in length to accommodate the depth and heights of production zones. To accommodate deployment of screens they are run in sections and connected on surface to match the height of the production zones.
In many wells there exists in one common well bore multiple production formations that are perforated or otherwise left open hole to allow simultaneous production from several formations at varying depths into the well bore and up the production casing. Often in these multiple production formations wells the different formations in the earth are separated by lithology that does not have productive fluids often times due to lower permeability and porosity. With the current art these varying production formations are completed simultaneously and flow into a common production tubing to surface. It often occurs that one productive formation will produce less fluids, or unwanted fluids, or for resource management reasons the varying formations may be more desirably produced at different flow rates or be produced at different times. In the case of gravel packed wells the methods to shut of production from a formation in a well with multiple production formations producing simultaneously into a common well bore requires mechanical well intervention techniques none to those familiar to the art. These intervention techniques can include, squeeze cementing, the setting of plugs via wireline and rig methods, and the pulling of production tubing, control lines, electrical cable, packers, sleeves and other disposed subterranean devices in the well. The above prior art techniques require mechanical intervention into the well with pipes, wireline, or pumped chemicals into the well bore to affect the inflow of fluids into and through screen systems.
U.S. Pat. No. 5,447,201 discloses an adjustable fluid inflow assembly for an oil or gas well where the influx of fluids from a plurality of annular inflow zones is controlled by a series of annular disk shaped valves which are each arranged between a downstream end of each inflow zone and a production tubing passing therethrough.
A disadvantage of the known assembly is that all fluid entering an annular inflow zone needs to be discharged through an annular disk shaped valve and the fluid flow rate in each valve is therefore high which causes a high rate of wear of the valve. The current invention aims to alleviate this and other disadvantages of the known well inflow control assembly such that production formations can be shut off or their fluid production reduced from production zones by non-intervention methods from surface.